Add Media Router issue-banner.

chrome/browser/resources/media_router/elements/issue_banner/issue_banner.html

+<link rel="import" href="chrome://resources/polymer/polymer/polymer.html">
+<polymer-element name="issue-banner">
+<template>
+  <link rel="stylesheet" href="issue_banner.css">
+  <template if="{{issue.isBlocking}}">
+    <div class="blocking-issue-header">
+      <div class="sad-face"></div>
+      <div>
+        <span class="blocking-issue-title">{{issue.title}}</span>
+        <span class="blocking-issue-message">{{issue.message}}</span>
+      </div>
+    </div>
+    <div>
+      <template if="{{issue.optActionText}}">
+        <button class="button-secondary" title="{{issue.optActionType}}"
+            on-click="{{onClickAction}}">
+          {{issue.optActionText}}
+        </button>
+      </template>
+      <button class="button-action" title="{{issue.defaultActionType}}"
+          on-click="{{onClickAction}}">
+        {{issue.defaultActionText}}
+      </button>
+    </div>
+  </template>
+  <template if="{{!issue.isBlocking}}">
+    <div class="non-blocking-issue">
+      <span>{{issue.message}}</span>
+      <br/>

[James Hawkins, 2015/04/06 21:52:47]

Don't use <br>.  Adjust margins instead (although the fact that you're using a
span for the text above makes me think you just want a line break here, so use
<div> instead of <span>).

[apacible, 2015/04/06 22:50:41]

Done. Also updated above <spans> to <div> so I don't need to use display: block;
on the css.

+      <template if="{{issue.optActionText}}">
+        <span class="issue-action" title="{{issue.optActionType}}"
+            on-click="{{onClickAction}}">
+          {{issue.optActionText}}</span>
+      </template>
+      <span class="issue-action" title="{{issue.defaultActionType}}"
+          on-click="{{onClickAction}}">
+        {{issue.defaultActionText}}</span>

[James Hawkins, 2015/04/06 21:52:48]

nit: Move </span> to a new line.

[apacible, 2015/04/06 22:50:41]

Done. Moved above one as well.

+    </div>
+  </template>
+</template>
+<script src="issue_banner.js"></script>
+</polymer-element>